1. Field of the Invention
This invention relates to water soluble cores, a process for producing the water soluble cores, and a process for die casting metal at high pressure using the water soluble cores.
2. Description of the Related Art
JP-A 61-118350(1986) discloses a process for producing a water soluble core, which comprises casting a particulate material containing NaCl as a main ingredient under a pressure and calcining the casting.
JP-B 48-39696(1973) and JP-B 49-15140(1974) disclose processes for producing water soluble cores, which comprise melting a particulate material containing NaCl as a main ingredient and introducing the melted material into a die.
In the process of JP-A 61-118350, however, it is difficult to produce a core having a complex shape. In the processes of JP-B 48-39696 and JP-B 49-15140, there may be a problem that it is difficult to obtain a die casting having high quality because of a change of a core size or a crack in the core caused by contraction during solidification of the melted material.
Since the cores obtained by the aforementioned processes have a high density, it takes a long time to dissolve them when washing out from a die casting. And if a part of the core remains on the die casting, it may cause corrosion of the die casting.